CARRABASSETT VALLEY, Maine — Sugarloaf Mountain is celebrating its 60th anniversary as a ski resort, and thousands call Maine’s second-highest peak their home mountain. For as long as skiers have hit the slopes there, they’ve looked longingly to the east and wondered “what if?”

What if the neighboring mountain were open to skiing, too?

“We’ve been talking about Burnt Mountain for 59½ years,” Sugarloaf General Manager John Diller said at a press conference Tuesday.

The talking is over.

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Diller and Steve Kircher, president of Boyne East, unveiled a plan to open Burnt Mountain to skiers and snowboarders this winter. When the three-phase plan is complete in three to six years, the addition will have doubled the skiable acreage at Sugarloaf from 651 acres to 1,306 acres.

More important from a marketing point of view: The additional space will give it a cachet Sugarloafers have been waiting for.

“I said before, the possibility of becoming the largest ski area east of the Rockies [which Sugarloaf will become when the project is completed] is a huge moment in time for this ski area and for Maine,’’ Kircher said. “It’s the bragging rights of everything you want at a ski area and a destination. I know the stories of people talking about going to Burnt Mountain, going to Burnt Mountain. We’re finally going to Burnt Mountain and it’s starting [with tree-cutting efforts] … on Monday.’’

Burnt Mountain is 3,595 feet tall — slightly shorter than Sugarloaf’s 4,237 feet — and the project won’t turn it into a clone of its bigger brother.

Sugarloaf will neither make snow on nor groom Burnt Mountain, and only select trees will be cut. Instead, visitors will enjoy a backcountry, or “side-country,’’ experience, skiing through wooded glades. But while the experience will seem remote and wild, Sugarloaf also will station ski patrollers on Burnt Mountain.

Kircher said that in the future, tens of thousands of additional skiers may visit Sugarloaf to sample the pristine, gladed conditions.

The project will move forward in three phases.

The first phase adds a 270-acre swath of mountain called “Brackett Basin.’’ That area will be open this winter.

Next up is a 135-acre parcel that will provide accessibility to the summit of Burnt Mountain and an above-treeline experience. The third phase adds yet another 250 acres on Burnt Mountain’s north face.

Diller and Kircher indicated that the plan originally was viewed as a three-year process, but both admitted that the total assimilation of the 655-acre Burnt Mountain lands might take as long as five or six years.

According to a Sugarloaf press release, the expansion would feature many different types of terrain, including “tight, steep eastern-tree skiing to wide-open western-style glades.’’

Skiers and snowboarders will access the Burnt Mountain parcels from existing lifts, though Diller said the resort may choose to add snow cat service as well. An additional lift — perhaps a decommissioned T-bar that runs on a diesel engine — could also be added.

Kircher is excited about the prospects for the future.

“This is a huge expansion. This is going to be done in a way that will be both environmentally friendly and aesthetically pleasing to those who come here, and much more exciting than any terrain probably that’s been unveiled in the East,’’ Kircher said.

Kircher said backcountry and side-country skiing is taking off around the world, and Sugarloaf is following that trend.

“It’s a really exciting niche that is expanding and is certainly where the growth of the industry has gone,’’ Kircher said.

Because the resort will not have to make or groom snow, and will rely on existing lifts, Kircher said the move will be cost-effective and add skiing options for a moderate investment. Diller said the sale of trees from the land that is thinned will help the resort’s bottom line.

And though both men want the project to move forward as quickly as possible, Kircher said that making the right choices is more important than making the quickest or easiest ones.

“You’ve got to do it right. And doing it right doesn’t mean sending 60 guys out there, or gals, with chain saws, and having them do it in a way that could be detrimental to the long-term skiability of it, and taking down trees that should stay,’’ Kircher said.